Electrolyte leakage management in an electrochemical cell

ABSTRACT

Described herein are methods, air cathodes or electrochemical cell systems configured to reduce or alleviate leakage of electrolyte within air cathodes. A method for electrolyte leakage management in an electrochemical cell system includes: configuring a plurality of air cathodes within an electrochemical cell system, each of the plurality of air cathodes comprising a frame, a membrane oxygen electrode attached to the frame to define a sealed interior cavity, an air inlet communicative with the interior cavity, a liquid outlet communicative with the interior cavity; positioning the liquid outlet lower than the air inlet; and draining electrolyte leakage from the interior cavity through the liquid outlet. An electrochemical cell system configured for electrolyte leakage management includes: a housing; an electrolyte disposed in the housing; a metallic material, when positioned in the first spaces, forms one or more discharging anodes; one or more charging anodes and one or more charging cathodes at least partially immersed in the electrolyte; and one or more air cathodes immersed in the electrolyte and one or more first spaces between the oxygen cathodes, each of the one or more air cathodes comprising 1) a frame, 2) a membrane oxygen electrode attached to the frame to define an interior cavity, 3) an air inlet communicative with the interior cavity, 4) an air outlet communicative with the interior cavity, 5) a liquid outlet communicative with the interior cavity, 6) the liquid outlet positioned lower than the air inlet.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an air cathode, and more particularlyrelates to air cathodes for use in electrochemical power sources such asfuel cells or batteries.

Description of the Related Art

Metal-air, particularly zinc-air, electrochemical systems have been seenas promising technologies for low cost large scale energy storage. Therehave been continuous attempts to develop energy storage systems based onzinc-air chemistry including rechargeable batteries, mechanically andhydraulically rechargeable fuel cells (see review articles by X. G.Zhang: “Zinc Electrodes”, and S. Smedley and X. G. Zhang, “Zinc-Air:Hydraulic Recharge”, in Encyclopedia of Electrochemical Power Sources,Eds. Jungen Garche etc., Amsterdam: Elsevier, 2009).

Electrically rechargeable metal-air batteries have high energy density.Technical problems can include degradation of the bi-functional aircathode and the detrimental change of the morphology of metal anodeduring cyclic discharging and charging.

For metal-air fuel cells, the metallic active anode material is likefuel and can be generated and regenerated by electro deposition. Thegeneration of metallic material by electro deposition serves thefunction of storing electricity. The deposited metallic materialtogether with electrolyte in liquid form is fed or fueled into the fuelcells, which serves the function of generating electricity from thestored energy in the metallic material.

Regenerative metal-air fuel cell systems have advantages overrechargeable battery systems such as independent scaling of power andcapacity and continuous discharging without interruption for charging.Technical problems can include clogging or jamming during fueling ortransporting the zinc materials into and out the electrochemical cellsand uneven distribution of the materials within a cell and between thecells.

PCT Publication WO2015/028887 (published 5 Mar. 2015) disclosed severalfunctional solutions to benefit electrochemical power sources such asrechargeable batteries, regenerative fuel cell systems and/or redox flowbatteries—one such functional solution being a novel air cathodecomprising a frame covered with one or more oxygen membrane electrodes,a cavity enclosed by the oxygen membrane electrode(s), one or moreseparators covering the surface of the oxygen membrane electrode(s), andan inlet and an outlet for passing air or an oxygen-containing gas intoand out of the cavity. This novel air cathode advantageously functionsto allow independent removal of an individual air cathode withoutaffecting other cathodes in the discharging assembly, and thus allowingconvenient changing of cathodes or cleaning of the cell container whenneeded.

Development of this air cathode has potential to yield furtherimprovements.

As electricity storage is an important enabling technology for effectiveuse of renewable energy sources and such technology is prioritized bygovernment and industry alike, there is a continuing need forimprovements to or alternatives to conventional air cathodes.

SUMMARY OF THE INVENTION

In an aspect there is provided, an air cathode comprising: a frame; amembrane oxygen electrode attached to the frame to define an interiorcavity; an air inlet communicative with the interior cavity; an airoutlet communicative with the interior cavity; a liquid outletcommunicative with the interior cavity; the liquid outlet positionedlower than the air inlet.

In another aspect there is provided, an air cathode comprising: a framecomprising a convex top surface; a single membrane oxygen electrodeattached to first and second opposing sides of the frame and attached tothe convex top surface in between the first and second opposing sides ofthe frame to define an interior cavity; an air inlet communicative withthe interior cavity; an air outlet communicative with the interiorcavity.

In another aspect there is provided, a method for electrolyte leakagemanagement of an air cathode in an electrochemical cell systemcomprising: configuring an air cathode comprising a liquid outlet asdescribed herein within an electrochemical cell system; and drainingelectrolyte leakage through the liquid outlet.

In another aspect there is provided, a method for electrolyte leakagemanagement in an electrochemical cell system comprising: configuring aplurality of air cathodes within an electrochemical cell system, each ofthe plurality of air cathodes comprising a frame, a membrane oxygenelectrode attached to the frame to define a sealed interior cavity, anair inlet communicative with the interior cavity, a liquid outletcommunicative with the interior cavity; positioning the liquid outletlower than the air inlet; and draining electrolyte leakage from theinterior cavity through the liquid outlet.

In another aspect there is provided, an electrochemical cell system,comprising: a container housing the electrochemical cell system; anelectrolyte disposed in the container; a plurality of air cathodesimmersed in the electrolyte and a plurality of first spaces between theair cathodes, each of the air cathodes comprising 1) a frame, 2) amembrane oxygen electrode attached to the frame to define an interiorcavity, 3) an air inlet communicative with the interior cavity, 4) anair outlet communicative with the interior cavity; a mechanism fordrainage of electrolyte leaked into the interior cavity of air cathodescomprising 1) a reservoir, 2) a liquid outlet communitive with theinterior cavity and with the reservoir, 3) a pump communitive with thereservoir and with the housing through a tubing; and a metallicmaterial, when placed in the first spaces, forms one or more discharginganodes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of an electrochemical cell including a pluralityof charging anodes and cathodes configured to form a charging assemblyand a plurality of air cathodes configured to form a dischargingassembly;

FIG. 2A shows a side view, FIG. 2B shows a top view and FIG. 2C showsvarious cross-section views of an air cathode frame having aconvex-shaped top surface;

FIGS. 2D and 2E show the air cathode frame with attachment of a singlemembrane oxygen electrode (2D and 2E) and a separator (2E);

FIG. 3 shows a side view of a variant air cathode frame having aconvex-shaped top surface;

FIG. 4 shows a side view of an air cathode frame including a liquidoutlet;

FIG. 5 shows a side view of a variant air cathode frame including aliquid outlet;

FIGS. 6A, 6B, 6C, and 6D each show a side view of further variants of anair cathode frame including a liquid outlet;

FIG. 7 shows a side view of another variant air cathode frame includinga liquid outlet;

FIG. 8A shows a side view and FIG. 8B shows a cross-section view ofanother variant air cathode frame including a liquid outlet;

FIG. 9A shows a side view and FIG. 9B shows an end view of a pluralityof air cathodes—each including a liquid outlet communicative with areservoir—installed as a discharging assembly in an electrochemical cellsystem; FIG. 9C shows the electrochemical cell system with a pumpinstalled to return liquid from the reservoir to a container of theelectrochemical cell system; FIG. 9D shows a variant configuration ofthe electrochemical cell system shown in FIG. 9C; FIG. 9E shows anothervariant configuration of the electrochemical cell system shown in FIG.9C; FIG. 9F shows another variant configuration of the electrochemicalcell system shown in FIG. 9C;

FIG. 10 shows a cross-section view of a sealing mechanism for passingtubing through a side wall of a container of an electrochemical cellsystem;

FIG. 11A shows an end view and FIG. 11B shows a side view of a pluralityof air cathodes—including manifold configuration of liquid outlets andmanifold arrangement of air inlets—installed as a discharging assemblyin an electrochemical cell system;

FIG. 12 shows a side view of a variant configuration of the manifold andair cathode arrangement shown in FIG. 11B.

FIG. 13A shows an end view and FIG. 13B shows a side view of a pluralityof air cathodes—including manifold configuration of liquid outlets andmanifold arrangement of air inlets—installed as a discharging assemblyin a variant configuration of the electrochemical cell system shown inFIG. 9F.

FIG. 14A shows an end view and FIG. 14B shows a side view of a variantconfiguration of the electrochemical cell system shown in FIGS. 13A and13B.

FIG. 15A shows an end view and FIG. 15B shows a side view of a variantconfiguration of the electrochemical cell system shown in FIGS. 14A and14B.

FIG. 16 shows a block diagram of an illustrative example of a method ofelectrolyte leakage management in an electrochemical cell.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to the drawings, improvements to air cathodes will now bedescribed. An air cathode typically comprises a frame covered with oneor more oxygen membrane electrodes, a cavity enclosed by the oxygenmembrane electrode(s), one or more separators covering the surface ofthe oxygen membrane electrode(s), and an inlet and an outlet for passingair or an oxygen-containing gas into and out of the cavity. As the aircathode can be operational with air or any gas of suitable oxygenconcentration (partial pressure), the air cathode may be referred to asan oxygen cathode, and the terms air cathode and oxygen cathode may beused interchangeably. Oxygen membrane electrode may also be referred toas gas diffusion electrode in the field.

An example of an operational environment of an air cathode, as installedin electrochemical cell 100, is shown in FIG. 1—previously described ingreater detail in PCT Publication WO2015/028887 (published 5 Mar. 2015)and briefly summarized here to provide operational context.

The electrochemical cell 100 includes a charging assembly 200, adischarging assembly 300, an electrolyte 400, a housing or container110.

The charging assembly 200 is located on the top section of the container110 above the discharging assembly. The charging assembly 200 comprisesone or more charging cathodes 230 and anodes 220, (two cathodes andthree anodes are illustrated in the figures for simplicity). Thecharging cathodes and anodes are appropriately spaced to match a layoutof the discharging assembly 300. The cathodes and anodes of the chargingassembly are physically secured on a horizontal bar 271 that provides asupport/substrate for maintaining position of the charging cathodes andanodes within container 110. Horizontal bar 271 is secured onto thecontainer 110 through an attachment fixture, for example and not limitedto a screw or aperture. The cathodes and anodes may alternatively bemounted directly on the cell container 110. The cathodes comprise aconductive material, for example and not limited to magnesium, that isstable in the electrolyte and has low adhesion to the deposited metallicmaterial.

During charging operation the metal in the electrolyte is reduced on thesurfaces of the cathodes forming metal deposit 501. As the deposits growon a surface of the charging cathode 230, they are periodicallydislodged from the surfaces and transported by gravity downward intofirst space 101 (each of the plurality of first spaces 101 defines anodebeds between two neighboring air cathodes 301 for containing fallenmetal deposit 501 to form a discharging anode 500) between the aircathodes 301 of the discharging assembly 300 underneath the chargingassembly. The metal deposits 501 may pile up into second space 102 tovariable heights above of the discharging assembly after the first space101 is filled. The first space 101 may also be described as that belowthe top edges of the air cathodes 301 or that amid of the air cathodesand the interior surface of the container for the case where the shapeof the air cathode is non-planar.

The discharging assembly 300, located beneath of the charging assembly200, comprises one or a plurality of air cathodes 301 (dischargingcathodes) with first space 101 defining an anode bed for containinganode 500 (discharging anodes) comprising the deposited metallicmaterial 501 fallen from the charging assembly. The current of theanodes is collected by any suitable anode current collector which are inturn communicative with any convenient set of bus and lead elements toconduct current to a terminal disposed to the outside of theelectrochemical cell 100. Similarly, the current of the air cathodes isconducted to a terminal disposed to the outside of the cell 100 byoperably communicative collector, bus and/or lead elements as suited toa particular implementation.

The discharging assembly 300 and the charging assembly 200 may be housedin the same body of electrolyte in a single container to form a cell,and the discharging assembly can be located underneath of the chargingassembly or on the side of the charging assembly. Alternatively, thedischarging assembly and charging assembly may be housed in separatecontainers as desired. But, regardless of the discharging assembly beinghoused in the container alone or in combination with the chargingassembly, the discharging assembly will be immersed in the same body ofelectrolyte such that the plurality of air cathodes 301 and theintervening first space(s) 101 are all immersed in the same body ofelectrolyte. The anodic electrode (negative electrode) of thedischarging assembly may be considered as consisting of one anode whenall the metallic material in the anode beds in the first spaces is acontinuous body of metallic material and alternatively may be consideredas a plurality of anodes when the anode beds are only partially filledby the metallic material.

The air cathode 301 in the discharging assembly 300 is a planarstructure with a cavity 302 as illustrated in FIG. 1. As described inPCT Publication WO2015/028887 (published 5 Mar. 2015) the air cathodecomprises a frame covered with two membrane oxygen electrodes that arepermeable to air but is impermeable to water. The surfaces of the oxygencathodes are covered with a separator to prevent direct contact betweenthe cathodes and anodes. The cavity 302 within the air cathode is forholding air or oxygen or a gas containing oxygen to allow the reductionof oxygen. The cavity is completely sealed except for an inlet and anoutlet to allow air or gas passing through.

The cell container 110 (or tank) can be made of plastic materials.Preferably, the container is made of a continuous piece of plasticmaterial with no discontinuity, such as holes and gaps, existing belowthe surface 401 of electrolyte such that there is no possibility ofelectrolyte leakage to outside of the cell. This is a particularadvantage over the conventional designs of metal-air cells, in which thesides of cell container are covered by air electrodes and are prone toleaking of electrolyte. The outer surface of the container may beconfigured as desired to support elements for electrical conduction, aircirculation or electrolyte circulation, such as terminals for electricalconduction, air inlet and outlet, a motor or an air pump. The dimensionand shape of the container 110 is determined according to the actualdesigns of the charging and discharging assemblies. The height of thecell container can be varied to change the space 102 (second space)without affecting the structures of the charging and dischargingassemblies of the cell. This flexible variation of the second space thatchanges the volume between the charging and the discharging assembliesallows for variation of energy storage capacities with only marginalimpact on the manufacturing and cost of the cell. As metallic materialcan be contained in the second space above the discharging assembly, thecell can have a large storage capacity or long runtime.

During the discharging operation of the cell, the anodes 500 areconsumed as the metal deposit is dissolved and the dissolved metal inthe electrolyte is transported out of the anode spaces with electrolytevia diffusion and convection and returns to the charging assembly. Thematerial 501 in the second space 102 above the anodes 500 falls into theanode spaces as the solid anode material is consumed, which maintainsthe electrochemical activity of the anodes.

At all times during an operational state, the air cathode will be atleast partially immersed in electrolyte 400. Therefore, liquid seal ofthe air cathode 301 is a significant consideration. It has beendiscovered that leaking of electrolyte 400 into cavity 302 can occurafter an extended period of use of the air cathode 301 in the cell 100.Thus, in numerous observed cases the air cathode 301 was initially freefrom leakage in testing and leakage occurs after extended use. It hasbeen observed that leakage tended to occur at places where the sealingwas weak or defective between the oxygen membrane electrode and aircathode frame. Electrolyte was also found to leak through the membraneoxygen electrode. Investigations identified that the leakage throughoxygen membrane electrode is due to defects (pinholes and large pores)across the surface of a membrane oxygen electrode, which may haveresulted from its manufacturing process. The defects can permit liquidto leak through the membrane oxygen electrode and into the enclosedcavity 302. Presence of defects and weak spots in membrane oxygenelectrodes cannot be fully prevented through quality control inspection,and therefore at present a small but significant percentage of oxygenmembrane electrodes are expected to contain a defect or weak spot thatcan allow leakage after a relatively short time of operation. The sizeof defects such as pinholes, dents, and the like and degree of weaknessof weak spots or areas can vary such that leakage tends to develop atdifferent time interval of operation. The time when first leaking isnoticeable in an air cathode varies with oxygen membrane electrode—someimmediately after the air cathode is placed into the electrolyte, someonly after weeks of discharging operation. The rate of leaking alsovaries, from slowly seeping through and forming a small droplet inseveral hours, to forming a droplet in seconds. It appears that many aircathodes eventually experiencing leaking. Thus, an effective solutionneeds to be developed in order for air cathodes to function continuouslyover time.

Solutions have been developed to address the potential for leakage intocavity 302.

A first solution is shown in FIGS. 2A to 2E. Sealing edges betweenmembrane oxygen electrodes and an air cathode frame are potentialsources of leaks. When first and second membrane oxygen electrodes areattached to opposing side faces of a frame, each membrane oxygenelectrode requires four sealing edges—two horizontal edges and twovertical edges. FIGS. 2D and 2E show a single membrane oxygen electrode350 covering both opposing side faces of frame 310 as well as a top ofthe frame 310, thus reducing horizontal sealing edges by half ascompared to the use of first and second membrane oxygen electrodes eachattached to one of the side faces. In addition to reducing potential forleaks, the integral coverage of top and both side surfaces of the frame310 achieved by the single membrane oxygen electrode 350 provides anadvantage of increasing the electrically active surface area of the aircathode as compared to the use of first and second membrane oxygenelectrode.

FIG. 2A shows a side view of air cathode frame 310, while FIG. 2B showsa top view of frame 310 and FIG. 2C shows various cross-sectional views(specifically views on cut-lines I-I, II-II, and III-III shown in FIG.2A). Frame 310 is bound by a border 312, the border configured as aU-shape with a bottom arm 312 a, and two substantially parallel andsubstantially co-extensive vertical arms 312 b, 312 c, and an inwardlyoriented top overhang extending from the top end of each vertical arm312 d, 312 e. Thus, opposing first and second top overhangs 312 d, 312 eextend co-axially inwardly toward each other from the top ends of firstand second vertical arms 312 b, 312 c, respectively. An air inlet 314 isdefined within the first top overhang 312 d, and an air outlet 315 isdefined within the second opposing top overhang 312 e. Both the airinlet 314 and the air outlet 315 are formed as a tubular aperture withineach top overhang, the tubular aperture configured to operably connectwith tubing communicative with an air source, including for example anair pump (not shown). Each tubular aperture extends through the topoverhangs 312 d, 312 e, providing fluid (ie., gaseous) communicationbetween an exterior of the air cathode and an interior cavity 302defined by frame 310.

A base plate 313 can be attached continuously to interior surfaces ofbottom arm 312 a, and vertical arms 312 b,c of border 312 as shown inFIG. 2A, or can connect intermittently to one or more arms of the border312 as desired. The base plate 313 may be non-porous as shown in FIG.2A, or may be perforated in any desired pattern. The base plate 313segments the interior cavity 302 defined by border 312. The base plate313 functions to support a plurality of ridges 311 that extend from baseplate 313. The plurality of ridges 311 are substantially co-planar withborder 312, so that the border 312 provides a sealing surface to attachto sealing edges of the single membrane oxygen electrode 350, whilecurved top edges 311 a and lateral edges 311 b of the plurality ofridges 311 combine to form an abutting support for the interior surfaceof the single membrane oxygen electrode 350, to reinforce and maintain aposition and shape of the single membrane oxygen electrode throughoutoperation.

FIGS. 2D and 2E show cross-section view I-I to illustrate attachment ofthe single membrane oxygen electrode 350 to frame 310, with the singlemembrane oxygen electrode 350 receiving abutting support from the curvedtop edges 311 a and lateral edges 311 b of the plurality of ridges 311.Curved top edges 311 a align with curved top surfaces of opposing firstand second co-axial top overhangs 312 d, 312 e, and therebyco-operatively support an inverted U-shaped or convex-shaped top bend ofthe single membrane oxygen electrode 350 in continuous sealed attachmentwith a first side of the frame, a top of the frame and a second side ofthe frame.

FIG. 2E additionally shows attachment of separator 351 to cover thesingle membrane oxygen electrode 350, and prevent direct contact withdischarging anodes 500 formed in first spaces 101 by dislodged/fallenmetal deposit 501. The separator 351 is a liquid permeable membrane thatfunctions to maintain a sufficient physical distance between anode andcathode surfaces to prevent electrical short circuits, while alsoallowing the transport of water and ionic charge carriers that areneeded to close the circuit during the passage of current in anelectrochemical cell. The separator is electrochemically stable withrespect to electrolyte, and both anode and cathode surfaces, and is ofsufficient mechanical strength to withstand tensioned attachment to theair cathode.

Membrane oxygen electrodes and separators are well known in the field ofelectrochemical power sources, and compatible combinations of membraneoxygen electrodes and separators may be selected as desired to suit aspecific implementation. Examples of membrane oxygen electrodes aredescribed in D. Linden, Handbook of Batteries, 3rd edition, McGraw-Hill,New York, 2002. Examples of separators are described in Rahman et al.(2013) “The Electrochemical Society High Energy Density Metal-AirBatteries: A Review” J. Electrochem. Soc., Vol. 160 (10): A1759-A1771.

The frame 310 can be manufactured as a single integral component, or maybe manufactured as separate border 312, base plate 313 and ridge 311components that are connected in a desired configuration.

While FIGS. 2A-2E show a specific variant of the frame 310 forillustrative purposes, it should be recognized that many other variantscan be readily implemented, and each variant may have many shapes andconfigurations. For example, as shown in FIG. 3, a continuous bordervariant of border 312 may be sufficient to form frame 310 a, without aneed for a base plate 313 and ridges 311—a continuous border variant canbe formed as a rectangular shape with opposing top 312 f and bottom 312a arms and opposing vertical side arms 312 b, 312 c, an air inlet 314formed in one of the arms, an air outlet 315 formed in one of the armsand the top arm 312 f having a semi-cylindrical convex top surface withwindows 320 or vent gratings optionally formed in the top arm to allowportions of the interior surface of the membrane oxygen electrodeabutting the semi-cylindrical convex top surface to be exposed to aircirculated within the enclosed cavity 302.

As the semi-cylindrical convex top surface of the top arm 312 f of thecontinuous border variant replaces the rounded support surface of thecombined co-aligned plurality of curved top edges 311 a of ridges 311, abase plate 313 and ridges 311 become optional. Many different variationsof the frame 310 are feasible provided that a rounded or curved supportis provided at the top edge of frame 310 to provide abutting support fora single membrane oxygen electrode 350 covering both opposing side facesof frame 310 as well as a top of the frame 310. The rounded or curvedtop surface shape of frame 310 supports an inverted U-shaped orconvex-shaped bend of the single membrane oxygen electrode 350 reducingmechanical strain on both the membrane itself and its attachment to theframe compared to a flat top surface shape of the frame.

Frame 310 a can include additional abutting support to reinforce andmaintain position of the membrane oxygen electrode provided by one ormore primary support bars 322 extending from an interior surface of theboarder 312, such as one or more horizontal, vertical or diagonal barsextending from one arm towards or to another arm. Furthermore, one ormore secondary support bars 324 may be optionally included to fortify orreinforce the one or more primary support bars 322. Primary support bars322 function to provide abutting support for the membrane oxygenelectrode, and therefore will often be sized and positioned to providefirst and second opposing surfaces that abut a membrane oxygen electrodein alignment with corresponding first and second opposing surfaces ofone or more of the arms of frame 310 a. A distance between first andsecond opposing surfaces of the arm of frame 310 a for contacting amembrane oxygen electrode will typically be substantially equal to thedistance between opposing surfaces of a membrane oxygen electrode acrossthe interior cavity 302 at a plane of contact with the arm. Similarly, adistance between first and second opposing surfaces of the primarysupport bar 322 for contacting a membrane oxygen electrode willtypically be substantially equal to the distance between opposingsurfaces of a membrane oxygen electrode across the interior cavity 302at the plane of contact with the primary support bar. Primary supportbars 322 may be oriented to direct air flow, and may be perforated asdesired to further modify air flow. Secondary support bars 324 functionto fortify or reinforce primary support bars 322 and therefore may notprovide any surface for abutting a membrane oxygen electrode. Asecondary support bar 324 will typically be a rod have a diameter sizethat is less than 80% of the distance between opposing surfaces of amembrane oxygen electrode across the interior cavity 302. Still furthervariants of frame 310 are contemplated.

Another solution to address the potential for leakage into cavity 302 isillustrated in FIGS. 4 to 8.

FIG. 4 shows a side view of air cathode frame 310 b, a variant of frame310 shown in FIG. 2A. Frame 310 b is the same as frame 310 in beingbound by a border 312, the border 312 configured as a U-shape with abottom arm 312 a, and two substantially parallel and substantiallyco-extensive vertical arms 312 b, 312 c, an inwardly oriented topoverhang 312 d, 312 e extending from the top end of each vertical arm312 b, 312 c, an air inlet 314 defined within the first top overhang 312d, an air outlet 315 is defined within the second opposing top overhang312 e, a base plate 313 attached to an interior surface of border 312,and a plurality of ridges 311 extending from base plate 313.

Frame 310 b differs from frame 310 in that it further includes a liquidoutlet 317 defined at or near a bottom end of vertical arm 312 c. Afurther difference is a clearance 318 formed as an opening in a portionof base plate 313 located at or near the bottom end of vertical arm 312c, clearance 318 operably communicative with liquid outlet 317. Thefunction of clearance 318 is to reduce obstruction of flow by base plate313 on liquid outlet 317.

The air inlet 314, the air outlet 315 and the liquid outlet 317 may allbe formed as tubular apertures through border 312 supporting flowbetween interior and exterior surfaces of border 312. The tubularaperture defining each outlet can be configured to operably connect withauxiliary components to control and/or collect flow, for example, tubingcommunicative with an air source, for example an air pump (not shown)for air inlet 314 or air outlet 315, and for example, tubingcommunicative with a reservoir and a pump (not shown) for liquid outlet317. Each of air inlet 314, air outlet 315, and liquid outlet 317 is atubular aperture that extends through border 312, providing fluidcommunication between any tubing operably connected to each outlet andthe interior cavity 302 defined by frame 310 a and its sealed enclosureby membrane oxygen electrode 350.

Air inlet 314, air outlet 315 and liquid outlet 317 can be positioned inmany different configurations on frame 310 and its variants, providedthat liquid outlet 317 is positioned at the same height or lower thanthe air inlet 314 and the air outlet 315; the distance between theliquid outlet 317 and bottom frame arm 312 a is less than or equal tothe distance between the air inlet 314 and bottom frame arm 312 a, aswell as less than or equal to the distance between the air outlet 315and bottom fame arm 312 a. For example, FIG. 5 shows a variant frame 310c including a border configured as a U-shape with a bottom arm 312 a,and two substantially parallel and substantially co-extensive verticalarms 312 b, 312 c, but without the inwardly oriented top overhangs 312d, 312 e extending from the top end of each vertical arm. Variant frame310 c further includes air outlet 314 defined at a central portion ofvertical arm 312 b operably communicative with clearance 318 formed asan opening in a corresponding portion of base plate 313, and a combinedair outlet and liquid outlet 316 defined at a bottom portion of verticalarm 312 c operably communicative with clearance 318 formed as an openingin a corresponding portion of base plate 313.

FIGS. 6A-6D show further examples of different configurations of airinlet, air outlet, and liquid outlet, all of which maintain a distancebetween the liquid outlet and the bottom arm of the frame that is lessthan or equal to corresponding distances for the air inlet or the airoutlet.

FIGS. 6A-6D also show examples of modification of ridge patterns todirect an air flow path 600 and achieve a desired air circulationthrough interior cavity 302 during operation. FIG. 6A shows acombination of surface features extending from base plate 313, includinga plurality of curved or rounded ridges 311 c (devoid of lateral edges311 b shown in FIGS. 2C and 2D) extending from a top edge of the baseplate 313, a ridge 311 having both curved edges 311 a and lateral edges311 b, and a plurality of posts 311 d arranged in a grid pattern of 7columns and 6 rows. FIG. 6B shows a combination of curved or roundedridges 311 c extending from a top edge of base plate 313 and diagonallyoriented ridges 311 e extending from an interior portion of base plate313. Diagonally oriented ridges 311 e are inclined/declined fromhorizontal to facilitate or direct electrolyte drainage towards theliquid outlet 317. FIGS. 6C and 6D shows further configurations ofridges 311, 311 c and/or 311 d positioned in relation to air inlet andoutlet to promote a corresponding air flow path 600, and more generally,air circulation during operation.

FIG. 7 shows a further example of a frame including air inlet 314, airoutlet 315, and liquid outlet 317. Variant frame 310 d is similar tovariant frame 310 a shown in FIG. 4 in being devoid of a base plate 313and connected ridges 311, differing in that variant frame 310 d includesa diagonal gutter 330 to direct electrolyte drainage towards liquidoutlet 317. The diagonal gutter 330 is formed along an interior surfaceof bottom arm 312 a of border 312, the gutter 330 including a crestsurface 331 and a co-extensive trough 332, the trough having aninclined/declined orientation with the declined (lower) end of thetrough aligned with the liquid outlet 317 for fluid communicationbetween the gutter 330 and liquid outlet 317. The inclined (upper) endof the trough 332 abuts an interior surface of vertical arm 312 b ofborder 312, and the trough 332 continuously declines from vertical arm312 b to liquid outlet 317. Primary support bars 322 can extend from thecrest surface 331 within the interior cavity 302 and the primary supportbars 322 may be fortified or reinforced by a transverse secondarysupport bar 324. The gutter 330 may be formed with any desiredcrest/trough structure. For example, in lateral cross-section the gutter330 may be U-shaped or concave-shaped with two opposing crest surfaceand a central trough or the gutter may be wedge shaped with a singlecrest surface declining to a trough that is sized to abut the membraneoxygen electrode so that the electrode forms a wall of the gutter.

FIG. 8A shows a side view and FIG. 8B shows a cross-section view alongcut line IV-IV of another example of a variant frame supporting an aircathode that is placed along an interior surface of a side wall of cellcontainer 110. In this variant frame, ridges 311 are formed withoutcurved top edges 311 a as the membrane oxygen electrode is attached to asingle side and top of the variant frame. Therefore, the membrane oxygenelectrode is attached in a linear rather than curvilinear profile, andmore specifically does not make an inverted U-shaped or convex-shapedtop bend as typically seen when a single membrane oxygen electrodecontinuously attaches to a first side of the frame, a top of the frameand a second side of the frame as shown for example in FIGS. 2A-2E.Instead the variant frame shown in FIGS. 8A and 8B comprises a sloped ortapered portion at the top of the variant frame. The sloped top portionallows a smooth bordering with the sides of the cell container and mayhelp downward movement of the metallic materials along the sides of thecell container and down towards the first space located adjacent to theair cathode.

Whether air inlet, air outlet or liquid outlet are located at the top orside of frame 310 or any one of its variants, the shortest distance ofcommunicative tubing to the exterior surface of container 110 isprovided by passing the communicative tubing through a side wall of thecontainer 110. FIGS. 9A and 9B show an example of communicative tubingpassing through a side wall of the container 110. Tubing 361 a connectswith a port for air inlet 314, and tubing 361 a passes through a boreformed in side wall of container 110, with a sealing gasket or a sealingring 362 disposed within the bore that circumferentially seals tubing361 a to prevent electrolyte leakage through the bore, more particularlyto prevent leakage between the interior surface of the bore and theexterior surface of tubing 361 a. Similarly, tubing 361 b, as airoutlet, connects with a port for air outlet 315, and tubing 361 b passesthrough a bore formed in side wall of container 110, with a sealinggasket or sealing ring 362 disposed within the bore to circumferentiallyseal tubing 361 b to prevent electrolyte leakage through the bore, moreparticularly to prevent leakage between the interior surface of the boreand the exterior surface of tubing 361 b. Similarly, tubing 361 cconnects with a port for liquid outlet 317, and tubing 361 c passesthrough a bore formed in side wall of container 110, with a sealinggasket or a sealing ring 362 disposed within the bore tocircumferentially seal tubing 361 c to prevent electrolyte leakagethrough the bore, more particularly to prevent leakage between theinterior surface of the bore and the exterior surface of tubing 361 c.Tubing 361 c provides a defined flow path to a reservoir 370 designatedto collect electrolyte 400 drained from within interior cavity 302 ofair cathode 301. Reservoir 370 can be operably connected with furthertubing 356 and a pump 355 as desired to actively flow electrolyte fromreservoir 370 into container 110, as shown for example in FIG. 9C.Alternatively, tubing 361 c may be connected with a pump and tubing toprovide a defined flow path into container 110 so that drainedelectrolyte 400 may directly flow from liquid outlet 317 throughconnected tubing back into container 110 without use of an intermediatestorage container such as reservoir 370. In FIGS. 9A and 9C, drainedelectrolyte 400 collected in reservoir 370 is shown with a differentvisual pattern than the bulk body of electrolyte 400 inside container110 for illustrative purposes only to better visually distinguish thestructures of the reservoir 370 and the container 110, and it will beunderstood that the components of the drained electrolyte and the bulkbody of electrolyte remain the same and therefore both are designated byreference numeral 400.

The location of reservoir 370 may be varied. For example, FIG. 9D showsreservoir 370 placed outside and underneath container 110.

FIG. 9E further shows an embodiment where reservoir 370 is placed insidethe container 110 and tubing 361 c is also placed inside container 110connecting interior cavity 302 and the interior of reservoir 370. Inthis embodiment, tubing 356 passes through a bore formed in side wall ofcontainer 110, with a sealing gasket or ring 362 disposed within thebore to circumferentially seal tubing 356 to prevent electrolyte leakagethrough the bore, more particularly to prevent leakage between theinterior surface of the bore and the exterior surface of tubing 356.

FIG. 9F further illustrates a further embodiment where reservoir 370 isplaced inside the container 110 and tubing 361 c is also placed insidecontainer 110 connecting interior cavity 302 and the interior ofreservoir 370. In this embodiment, tubing 356 passes through a boreformed in side wall of container 110, with a sealing gasket or ring 362disposed within the bore to circumferentially seal tubing 356 to preventelectrolyte leakage through the bore, more particularly to preventleakage between the interior surface of the bore and the exteriorsurface of tubing 356. A tubing 357 connects the environment outside ofthe container 110 and the interior reservoir 370 and passes through abore formed in side wall of container 110, with a sealing gasket 362disposed within the bore to circumferentially seal tubing 357 to preventelectrolyte leakage through the bore, more particularly to preventleakage between the interior surface of the bore and the exteriorsurface of tubing 357. In this example, tubing 361 c functions as bothan air outlet and liquid outlet with the air entered in cavity 302passing through 361 c into the interior of reservoir 370 and thenpassing through tube 357 to the exterior of container 110.

FIG. 10 shows a more detailed sectioned view of the sealing mechanismfor passing tubing through a side wall of container 110. Tubing 361 aconnects with a port for air inlet 314 providing communicative air flowfrom an air pump (not shown) to the interior cavity 302 enclosed withinair cathode 301. Extending from within internal cavity 302 to theexterior of container 110, the tubing 361 a first passes through a portfor air inlet 314, with a sealing gasket 362 a disposed within the portto circumferentially seal tubing 361 a to prevent electrolyte leakagethrough the air inlet port into the interior cavity 302. Tubing 361 athen passes through a bore formed in side wall of container 110, with asealing gasket 362 disposed within the bore to circumferentially sealtubing 361 a to prevent electrolyte leakage through the bore to theexterior of the container 110.

FIG. 9B shows five air cathodes arranged in parallel with each aircathode connected to tubing extending outward through a bore in the sidewall of container 110, each bore equipped with a sealing gasket,resulting in a total of five bores for air inlets and five bores for airoutlets. The number of bores through the side walls of container 110 canbe reduced by collecting tubing within the container 110 in a manifoldand having a single tube extending from each manifold through a bore inthe side wall of the container 110. For example, as shown in FIGS. 11Aand 11B tubing communicative with air inlets of five air cathodes 301can each operably connect with manifold 700 a which is equipped with asingle tube to extend through a bore in a side wall of container 110 toconnect with an air pump as desired (not shown). Similarly, tubingcommunicative with air outlets of five air cathodes 301 can eachoperably connect with manifold 700 b which is equipped with a singletube to extend through a bore in a side wall of container 110 to connectwith an air pump as desired (not shown). Similar, manifold arrangementcan be configured for liquid outlets.

FIG. 12 shows that border 312 of air cathode 301 may be shaped asdesired with indents or pockets to accommodate manifolds 700 a, 700 b soas to maximize air cathode size and corresponding membrane oxygenelectrode surface area.

FIG. 13A shows an end view and FIG. 13B shows a side view of a pluralityof air cathodes—including manifold configuration of air outlets andliquid outlets and manifold arrangement of air inlets—installed as adischarging assembly in a variant configuration of the electrochemicalcell system shown in FIG. 9F.

Similar to FIG. 9F, FIGS. 13A and 13B illustrate an embodiment wherereservoir 370 is placed inside the container 110 and tubing 361 c isalso placed inside container 110 connecting interior cavity 302 and theinterior of reservoir 370. Tubing 361 c connects with a port forcombined air and liquid outlet 316 in air cathode 301, Tubing 361 cprovides a defined flow path to the reservoir 370 designated to collectelectrolyte 400 drained from within interior cavity 302 of air cathode301. Tubing 361 c provides both air flow and liquid flow from interiorcavity 302 of air cathode 301. Reservoir 370 is configured as a manifoldto receive each tubing 361 c from a plurality of air cathodes 301.Locating reservoir 370 and its communicative tubing inside container 110provides an advantage of allowing any unintended leakage (for example,from the reservoir 370 or from tubing connections) to be containedinside container 110.

FIGS. 13A and 13B differ from FIG. 9F, in that tubing to exhaust airflow and to remove drained electrolyte from reservoir 370 as well astubing to provide air flow to air inlet 314 passes through bores formedin a top lid of container 110 above the level of electrolyte 400. Thisarrangement of connecting tubing from respective inlets and outlets ofthe air cathodes to the exterior of container 110 requires greaterlengths of tubing compared to the arrangement shown in FIG. 9F, butbenefits from avoiding potential leakage of electrolyte from the boresin side walls of container 110 that could occur with the arrangementshown in FIG. 9F. More specifically, in this embodiment shown in FIGS.13A and 13B, reservoir 370 is operably connected to tubing 356 and apump 355 to actively flow the drained electrolyte collected in reservoir370 against force of gravity and out of the top surface of container 110in an ascending portion of tubing 356 and then back into container 110in the direction of flow marked by arrow 355 a in a descending portionof tubing 356. Ascending and descending portions of tubing 356 passthrough bores formed in a top lid of container 110 for exit from andreturn to the interior of container 110, and because the bores areformed in the top lid above the electrolyte top surface, a sealinggasket is optional and need not be disposed within the bores tocircumferentially seal tubing 356 to prevent electrolyte leakage. Atubing 357 connects the environment outside of the container 110 and theinterior reservoir 370 and also passes through a bore formed in top lidof container 110 to exhaust air flow from the reservoir 370, and again asealing gasket disposed within the bore to circumferentially seal tubing357 is optional as the bore is above the electrolyte top surface. Inthis example, tubing 361 c functions as both an air outlet and liquidoutlet with the air entered in cavity 302 passing through 361 c into theinterior of reservoir 370 and then passing through tube 357 to theexterior of container 110. Tubing communicative with air inlets 314 ofthe plurality of air cathodes 301 (for example, 5 air cathodes shown inFIG. 13A) can each operably connect with manifold 700 a which isequipped with a single tube 361 a to extend through a bore in a top lidof container 110 to connect with an air pump as desired—again a sealinggasket disposed within the bore to circumferentially seal tubing 361 ais optional as the bore is above the electrolyte top surface.

FIG. 14A shows an end view and FIG. 14B shows a side view of a pluralityof air cathodes—including manifold configuration of air outlets andliquid outlets and manifold arrangement of air inlets—installed as adischarging assembly in a variant configuration of the electrochemicalcell system shown in FIGS. 13A and 13B. FIGS. 14A and 14B illustrate anembodiment that is similar to the embodiment shown in FIGS. 13A and 13Bexcept that the manifold reservoir 370 is configured to abut and beco-extensive with a bottom side corner of container 110. FIGS. 13A and13B and FIGS. 14A and 14B are similar in that the reservoir 370 providesa manifold for receiving air flow exhaust and drained electrolyte fromthe interior cavity of the air cathode. FIGS. 13A and 13B and FIGS. 14Aand 14B differ in that FIGS. 13A and 13B shows the reservoir 370constructed as a chamber component that is positioned and affixedbetween the bottom of the air cathode 301 and the bottom of thecontainer 110 without abutting either of the bottom of the air cathode301 or the bottom of the container 110, while FIGS. 14A and 14B show thereservoir 370 abutting both the bottom of air cathode 301 and the bottomof the container. Reservoir 370 shown in FIGS. 14A and 14B, may beconstructed as desired to be an integrated formation of container 110 orto be a separate chamber component that is installed and affixed to thebottom side corner of the container 110.

FIG. 15A shows an end view and FIG. 15B shows a side view of a pluralityof air cathodes—including manifold configuration of air outlets andliquid outlets and manifold arrangement of air inlets—installed as adischarging assembly in a variant configuration of the electrochemicalcell system shown in FIGS. 14A and 14B. FIGS. 15A and 15B illustrate anembodiment that is similar to the embodiment shown in FIGS. 14A and 14Bexcept that the air inlet tubing 361 a and the air outlet tubing 357ascend within the interior of container 110 and exit from the interiorof the container 110 to the exterior of the container 110 through boresin the side wall of container 110 at a position in between theelectrolyte and the top lid (ie., a position above the electrolyte 400top surface and below the top lid of the container 110). manifoldreservoir 370 is configured to abut and be co-extensive with a bottomside corner of container 110. Although the liquid outlet tubing 356 isshown to exit and re-enter the container 110 through the top lid, theliquid outlet tubing 356 and associated pump 355 ay readily beconfigured to be positioned at a side wall similar to passage of tubing357 or passage of tubing 361 a through the side wall in between theelectrolyte top surface and the top lid.

Many cells have been constructed with air cathodes having a liquidoutlet providing a drainage hole at or near the bottom of the interiorcavity of the air cathodes so as to drain the electrolyte that leakedinto the interior cavity. The air cathodes of such cells have been foundto function continuously over time without being affected by the leakageof electrolyte.

Several illustrative variants have been described above. Furthervariants and modifications are described below. Moreover, guidingrelationships for configuring variants and modifications are alsodescribed below. Still further variants and modifications arecontemplated and will be recognized by the person of skill in the art.It is to be understood that guiding relationships and illustrativevariants or modifications are provided for the purpose of enhancing theunderstanding of the person of skill in the art and are not intended aslimiting statements.

The air cathode 301 is distinguished by requiring an interior cavity 302for air circulation, the interior cavity bound by interior surface ofthe border of a frame and by the interior surface of the membrane oxygenelectrode.

The air cathode can be operational with air or any gas of suitableoxygen concentration (partial pressure).

The air cathode typically comprises an air inlet and an air outlet forpassing air or an oxygen-containing gas into and out of the interiorcavity. However, if desired for a particular implementation the airinlet and air outlet can be configured in a single connection in the aircathode, for example, when pressurized air is provided as a duty cycleand escape of air occurs passively during an off portion of the dutycycle, or when air circulation is provided by a programmable reversibleair pump.

The air inlet and the air outlet can be independently connected to becommunicative with any one or more of conventional air flow controldevices, such as fans, air exchangers, air pumps, heat exchangers,dampers, valves, filters, sensors, dehumidifiers, moisture/water traps,regulators, or any other device for treatment of air, so that each ofthe air inlet and the air outlet are communicative with a separate airflow control device or separate combination of air control devices.Alternatively, the air outlet and the air inlet can be connected to thesame one or more air flow control devices so that control of air flowout of the air outlet and air flow into the air inlet is controlled bycommon single or combination of air control devices. As a furtheroption, if the air inlet and air outlet are connected to common aircontrol device(s), then at least part of the air flow from the airoutlet may be directed to the air inlet to create an air flow loop.

The air cathode may comprise a liquid outlet to drain electrolyte thatleaks into the interior cavity. Although not routine, leakage ofelectrolyte into the interior cavity may occur due to defects or weakspots at the time of manufacture or due to damage/erosion from extendedoperation, as for example a defect or weak spot in the membrane oxygenelectrode surface, a defect or weak spot in sealed attachment of themembrane oxygen electrode to the air cathode frame or a defect or weakspot in a seal of tubing though an inlet or outlet of the air cathode.The liquid outlet is not limited to a particular shape or configuration,except that it is positioned at the same level or lower than at leastone of the air inlet and the air outlet. Typically, the liquid outlet ispositioned at the same level or lower than both the air inlet and theair outlet. Typically, the liquid outlet is positioned lower than theair inlet. Often, the liquid outlet is positioned at or near the bottomof the air cathode. As electrolyte leaking into the interior cavity isdrawn down by gravity, positioning the liquid outlet at the same levelor lower than the air inlet and air outlet ensures that an accumulatedlevel of electrolyte leakage does not interfere with air flow at the airinlet or air outlet. Similarly, positioning the liquid outlet at or nearthe bottom of the air cathode can minimize accumulation of leakedelectrolyte that drips to the bottom of the air cathode by gravitationalforce. As the purpose of the liquid outlet is to drain unintendedelectrolyte leakage from within the interior cavity, the air cathodewill be devoid of a designated liquid inlet communicative with theinterior cavity.

Dimensions of the liquid outlet may differ from dimensions of the airinlet consistent with dimensions useful to achieve effective flow ofliquid as compared to gaseous material. For example, a diameter of theliquid outlet may be from about 2 millimeter (mm) to about 20 mm, whilea diameter of the air inlet may be from about 0.2 mm to about 10 mm.Similarly, dimensions of the liquid outlet may differ from dimensions ofthe air outlet, when the liquid outlet and the air outlet are twodifferent and distinct outlets. When the air outlet is distinct from theliquid outlet, the air outlet dimensions can be similar to dimensionsfor the air inlet, including for example a diameter of the air outletranging from about 0.2 mm to about 10 mm. When the air outlet and theliquid outlet are the same outlet, the dimensions of the air outlet willtypically follow dimensions useful to achieve effective flow of liquid.

Any convenient ridge or gutter shape and orientation may be installedwithin the interior cavity to direct leaked electrolyte towards theliquid outlet.

Frame 310 and its variants shown in the drawings, are generallyrectangular for the purpose of illustration only. Frame 310 need not belimited to a rectangular shape, and other shapes such as concave,convex, triangular, elliptical profiles are readily feasible. Frame 310can have many variations and each variant can have many configurationsprovided that sufficient support shaped as the semi-cylindrical convextop surface is provided for an inverted U-shaped or convex-shaped bendof the membrane oxygen electrode. The semi-cylindrical convex topsurface may be a single continuous surface as in frame 310 a for example(with optional windows 320, gaps, perforations, vent gratings, and thelike) or multiple co-aligned surfaces as in frame 310, 310 b or 310 c asexamples.

Ridges and primary support bars need not be rectangular—and could betriangular, elliptical, or any other profile as desired. Furthermoreridges and support bars need not be symmetric, as many asymmetric shapesare possible. Ridges and bars may be substituted with other supportstructures for example first and second vent grates that extend acrossfirst and second sides, respectively, of the interior of border 312,each of first and second vent grates providing a 90 degree curve at atop end to co-operate to form a semi-cylindrical convex top surface toprovide abutting support for the membrane oxygen electrode alongopposing side surfaces and a U-shaped or covex-shaped bend between theopposing side surfaces.

The border of the frame need not be rectangular, and many differentshapes are feasible for both its radial cross-section as well as itsoverall profile. The border of the frame can be shaped as desired toaccommodate a particular implementation, for example with/without liquidoutlet, or with/without indents to receive manifolds.

The border of the frame will typically house the air inlet, the airoutlet and/or the liquid outlet. Inlets and outlets provide an interfacefor a defined communicative flow path between an exterior of the aircathode and an interior cavity of the air cathode. Inlets and outletscan be shaped as desired and optionally equipped with sealing gaskets toprevent leakage through the inlet or outlet. Sealing gaskets may be anysealing structure including for example a sealing ring, or any othersealing material configured to sufficiently prevent or reduce leakagethrough the inlet or outlet. Sealing gaskets may be made of any suitablewater impermeable material including polymers, natural products, orcombinations thereof.

The inlets or outlets may also be optionally equipped with anyconventional component of flow conduits such as valves, filters,sensors, moisture/water traps, regulators and the like.

The frame components such as border, base plate, ridges and support barsmay be manufactured as a single piece or as separate components asdesired. The frame components may be made of the same material orseparate materials as desired. Frames may be manufactured in accordancewith conventional materials and general available methods of frameconstruction.

Many different membrane oxygen electrodes and separators may find usewithin the air cathode, and therefore the air cathode is not limited toany particular type of membrane oxygen electrode or separator, and mayaccommodate any combination of membrane oxygen electrode and separator.

Benefits provided by solutions described herein include for example,improved performance of an electrochemical cell. In absence of a leakagedraining solution, electrolyte leakage into air cathode can accumulateelectrolyte within the interior cavity of the air cathode compromising adischarging reaction and reducing current generation, thereby reducingperformance. Presence of a leakage draining solution provides aninterior cavity in which electrolyte accumulation is minimized orreduced so as to maintain current generation from the dischargingreaction. Another example of a benefit is improved longevity of theelectrochemical cell. In absence of a leakage draining solution,accumulation of leaked electrolyte into the interior cavity of aircathodes can compromise performance to the extent that theelectrochemical cell must be taken offline and refurbished with new aircathodes. Presence of a leakage draining solution provides air cathodesthat maintain sufficiently reduced levels of leaked electrolyte so as tomaintain operation of the electrochemical cell for a longer time frame.Another example of a benefit is a reduced time and cost of maintenance.In absence of a leakage draining solution, air cathodes must be checkedfor leakage upon noting a drop in performance and leaking air cathodesmust be replaced—identifying leaking air cathodes and installingreplacements can be time consuming and over time can result in asignificant operational cost. Presence of a leakage draining solutionallows for operation of an electrochemical cell without the time andcost needed to identify and replace leaking air cathodes. The leakagedraining solution allows for greater tolerance of defect or weak spots,and therefore manufacturing production yield.

Solutions described herein to reduce or alleviate leakage of electrolytemay provide benefits individually or in any combination.

Solutions described herein relate to an air cathode configured to reduceor alleviate electrolyte leakage. In a first illustrative example of anair cathode, the air cathode may comprise: a frame; a membrane oxygenelectrode attached to the frame to define an interior cavity; an airinlet communicative with the interior cavity; an air outletcommunicative with the interior cavity; a liquid outlet communicativewith the interior cavity; and the liquid outlet positioned lower thanthe air inlet.

Optionally in the air cathode, the frame comprises a border, the borderhousing the air inlet, the air outlet, and the liquid outlet. The bordermay comprise a bottom arm and first and second vertical side armsextending from opposing ends of the bottom arm. The border may comprisefirst and second opposing top overhangs extending co-axially inward fromcorresponding top ends of first and second vertical side arms. Theborder may comprise a top arm connecting corresponding top ends of firstand second vertical side arms. The liquid outlet may be formed in theborder at or near the bottom arm. The air inlet may be formed in one ofthe first and second opposing top overhangs. Alternatively, the airinlet may be formed in the border at or near the top arm.

Optionally in the air cathode, the frame comprises a base plateconnected to opposing interior surfaces of a border of the frame, and aridge extending perpendicularly from the base plate, the ridge orientedto direct liquid towards the liquid outlet. As another option, the framecomprises a gutter connected to an interior surface of a bottom borderof the frame, an end of the gutter communicative with the liquid outlet.

Typically, in the air cathode, the liquid outlet is positioned lowerthan the air outlet. In some examples, the air outlet and the liquidoutlet is the same. In an example, the diameter of the liquid outlet isbetween 2 mm to 10 mm. In a more specific example of the air cathode,the diameter of the air inlet is between 0.2 mm to 5 mm.

In a second illustrative example of an air cathode, the air cathode maycomprise: a frame comprising a convex top surface; a single membraneoxygen electrode attached to first and second opposing sides of theframe and attached to the convex top surface in between the first andsecond opposing sides of the frame to define an interior cavity; an airinlet communicative with the interior cavity; an air outletcommunicative with the interior cavity.

Optionally in the air cathode, the frame comprises a border, the borderhousing the air inlet, and the air outlet. As another option, the bordermay comprise a bottom arm and first and second vertical side armsextending from opposing ends of the bottom arm, the top ends of thefirst and second vertical side arms having a convex shape.Alternatively, the border may comprise first and second opposing topoverhangs extending co-axially inward from corresponding top ends offirst and second vertical side arms, the top surfaces of the first andsecond opposing top overhangs having a convex shape. Alternatively, theborder may comprise a top arm connecting corresponding top ends of firstand second vertical side arms, the top surface of the top arm having aconvex shape.

Optionally, in the air cathode, the frame comprises a base plateconnected to opposing interior surfaces of the border, and a pluralityof ridges extending from the base plate, each of the plurality of ridgeshaving a curved top edge that forms part of the convex top surface.

Solutions described herein relate to an electrochemical cell systemconfigured to reduce or alleviate electrolyte leakage of air cathodes.In a first illustrative example of an electrochemical cell system, theelectrochemical cell system may comprise: a housing; an electrolytedisposed in the housing; a metallic material, when positioned in thefirst spaces, forms one or more discharging anodes; one or more charginganodes and one or more charging cathodes at least partially immersed inthe electrolyte; and one or more air cathodes immersed in theelectrolyte and one or more first spaces between the oxygen cathodes,each of the one or more air cathodes comprising 1) a frame, 2) amembrane oxygen electrode attached to the frame to define an interiorcavity, 3) an air inlet communicative with the interior cavity, 4) anair outlet communicative with the interior cavity, 5) a liquid outletcommunicative with the interior cavity, 6) the liquid outlet positionedlower than the air inlet.

In a second illustrative example of an electrochemical cell system, theelectrochemical cell system may comprise: a housing; an electrolytedisposed in the housing; a plurality of oxygen cathodes immersed in theelectrolyte and a plurality of first spaces between the oxygen cathodes,each of the oxygen cathodes comprising 1) a frame, 2) a membrane oxygenelectrode attached to the frame to define an interior cavity, 3) an airinlet communicative with the interior cavity, 4) an air outletcommunicative with the interior cavity, 5) a liquid outlet communicativewith the interior cavity, 6) the liquid outlet positioned lower than theair inlet; a metallic material, when placed in the first spaces, formsone or more discharging anodes; and a second space above the dischargingcathodes for storing the excess metallic material when the first spaceis filled.

In a third illustrative example of an electrochemical cell system, theelectrochemical cell system may comprise: a housing; an electrolytedisposed in the housing; a plurality of oxygen cathodes immersed in theelectrolyte and a plurality of first spaces between the oxygen cathodes,each of the oxygen cathodes comprising 1) a frame, 2) a membrane oxygenelectrode attached to the frame to define an interior cavity; amechanism for drainage of electrolyte leaked into the interior cavity ofoxygen cathodes comprising 1) a reservoir, 2) an outlet communitive withthe interior cavity and with the reservoir, 3) a pump communitive withthe reservoir and with the housing through a tubing; a metallicmaterial, when placed in the first spaces, forms one or more discharginganodes; and a second space above the discharging cathodes for storingthe excess metallic material when the first space is filled.

In a fourth illustrative example of an electrochemical cell system, theelectrochemical cell system may comprise: a container housing theelectrochemical cell system; an electrolyte disposed in the container; aplurality of air cathodes immersed in the electrolyte and a plurality offirst spaces between the air cathodes, each of the air cathodescomprising 1) a frame, 2) a membrane oxygen electrode attached to theframe to define an interior cavity, 3) an air inlet communicative withthe interior cavity, 4) an air outlet communicative with the interiorcavity; a mechanism for drainage of electrolyte leaked into the interiorcavity of air cathodes comprising 1) a reservoir, 2) a liquid outletcommunitive with the interior cavity and with the reservoir, 3) a pumpcommunitive with the reservoir and with the housing through a tubing; ametallic material, when placed in the first spaces, forms one or moredischarging anodes; and a second space above the air cathodes forstoring the excess metallic material when the first space is filled.

Optionally, in the electrochemical cell system, the frame of each aircathode comprises a base plate connected to opposing interior surfacesof a border of the frame, and a ridge extending perpendicularly from thebase plate, the ridge oriented to direct liquid towards the liquidoutlet.

In another option for the electrochemical cell system, the frame of eachair cathode comprises a gutter connected to an interior surface of abottom border of the frame, an end of the gutter communicative with theliquid outlet.

In further options for configuring air cathodes in the electrochemicalcell system, the liquid outlet is positioned lower than the air outlet.In certain examples, the air outlet and the liquid outlet is the same.In other examples, the liquid outlet is positioned at or near the bottomof each air cathode. In further examples, the air inlet and the liquidoutlet are formed in a border of the frame.

Solutions described herein can be implemented as a method. In a firstexample of method, a method for drainage of liquid within an air cathodein an electrochemical cell system may comprise configuring an aircathode comprising a liquid outlet as described herein within anelectrochemical cell system, and draining liquid through the liquidoutlet.

In a second example of method, a method for drainage of liquid within anair cathode in an electrochemical cell system may comprise configuringan air cathode within an electrochemical cell system, the air cathodecomprising a sealed interior cavity, an air inlet communicative with theinterior cavity, a liquid outlet communicative with the interior cavity,the liquid outlet positioned lower than the air inlet, and drainingliquid through the liquid outlet.

In a third example of a method, a method for drainage of liquid withinan air cathode may comprise configuring an air cathode comprising aliquid outlet as described herein, and draining liquid through theliquid outlet.

In a fourth example of a method, a method for drainage of liquid withinan air cathode may comprise configuring an air cathode with a frame, amembrane oxygen electrode attached to the frame to define an interiorcavity, an air inlet communicative with the interior cavity, a liquidoutlet communicative with the interior cavity, the liquid outletpositioned lower than the air inlet, draining liquid through the liquidoutlet.

In a fifth example of a method, a method for electrolyte leakagemanagement in an electrochemical cell system may comprise configuring aplurality of air cathodes within an electrochemical cell system, each ofthe plurality of air cathodes comprising a frame, a membrane oxygenelectrode attached to the frame to define a sealed interior cavity, anair inlet communicative with the interior cavity, a liquid outletcommunicative with the interior cavity; positioning the liquid outletlower than the air inlet; and draining electrolyte leakage from theinterior cavity through the liquid outlet.

Methods include core features of configuring an air cathode defining aninterior cavity with both an air inlet and a liquid outlet communicativewith the interior cavity (502), positioning the liquid outlet at orlower than the air inlet (504), and draining electrolyte leakage fromthe interior cavity of the air cathode through the liquid outlet (506)as schematically indicated for an illustrative method example (500)shown in FIG. 16.

Methods optionally further comprise positioning an air outlet at orabove the liquid outlet. Methods optionally further comprise positioningthe air outlet at a same level as the liquid outlet, with a furtheralternative being that the liquid outlet and the air outlet arecoincident and coextensive so as to form a combined liquid and airoutlet. Methods optionally further comprise positioning the liquidoutlet at or near the bottom of the air cathode. Methods optionallyfurther comprise forming the air inlet and the liquid outlet are formedin a border of the frame of the air cathode.

Methods optionally further comprise flowing air to the air inlet (508)from an exterior of a container housing the electrochemical cell systemand exhausting air from the air outlet (510) to an the exterior of thecontainer. Air flow to the air inlet, and exhaust from the air outletcan be achieved through any suitable mechanism including, for example,connecting the air inlet to an air pump (512) and connecting the airoutlet to an air pump (514). The air inlet and the air outlet may beindependently communicative with different air pumps, or in otherexamples the air inlet and the air outlet may be communicative with thesame air pump.

Methods optionally further comprise collecting the electrolyte leakagedrained from the interior cavity through the liquid outlet into areservoir (516) that is isolated from an operational body of electrolytecirculating within a container housing the electrochemical cell. Thereservoir may be located within an interior of the container of theelectrochemical cell system for a desired implementation. The reservoirmay be located exterior to the container of the electrochemical cellsystem for a desired implementation. Methods optionally further compriseconfiguring the reservoir as a manifold to receive and collect theelectrolyte leakage drained from all of the plurality of air cathodes.

Methods optionally further comprise pumping the drained electrolyteleakage out from the reservoir with a pump communicative with thereservoir (518), and optionally the drained electrolyte leakage ispumped out from the reservoir and into the operational body ofelectrolyte circulating within the container (520). Alternatively,methods optionally further comprise pumping the drained electrolyteleakage out from the interior cavity of the air cathode with a pumpcommunicative with the liquid outlet of the air cathode, and optionallythe drained electrolyte leakage is pumped out from the interior cavityof the air cathode and into the operational body of electrolytecirculating within the container.

Collecting drained electrolyte leakage in a reservoir or manifold andadding the collected electrolyte leakage to the operational body ofelectrolyte benefits both electrolyte leakage management of air cathodesand maintaining suitable volume of the operational body of electrolyte.As such, methods comprising a step of collecting liquid drained from theliquid outlet in a reservoir or manifold communicative with the liquidoutlet and a step of pumping liquid out from the reservoir with a pumpcommunicative with the reservoir offer a convenient recycling ofelectrolyte leakage compared to a method of draining electrolyte leakageto a disposal unit. Methods may optionally comprise a step of pumpingliquid out from the reservoir and into a cell container of theelectrochemical cell system. Methods may optionally comprise a step ofpumping liquid out from the interior cavity of the air cathode with apump communicative with the liquid outlet of the air cathode. Methodsmay optionally comprise a step of pumping liquid out from the interiorcavity of the air cathode and into a cell container of theelectrochemical cell system. The step of pumping liquid out from thereservoir or the interior cavity of the air cathode may have anyconvenient cyclic or acyclic repetitive occurrence as desired for aspecific implementation.

Directional terms such as lower, upper, vertical, horizontal,perpendicular, parallel, incline, decline, direction of gravity,ascending, descending, above, below, top, bottom, side, front, rear, areintended to be interpreted in context of the air cathode in anelectrochemical cell in an operational position and configuration asshown for example in FIG. 1.

Approximating terms such as generally and substantially are intended todescribe variation that is close or near to a desired value or target,and such terms are intended to encompass variation that is at or near adesired value or target.

Embodiments described herein are intended for illustrative purposeswithout any intended loss of generality. Still further variants,modifications and combinations thereof are contemplated and will berecognized by the person of skill in the art. Accordingly, the foregoingdetailed description is not intended to limit scope, applicability, orconfiguration of claimed subject matter.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. (canceled) 6.(canceled)
 7. (canceled)
 8. (canceled)
 9. (canceled)
 10. (canceled) 10.(canceled)
 12. (canceled)
 13. (canceled)
 14. (canceled)
 15. (canceled)16. (canceled)
 17. (canceled)
 18. (canceled)
 19. (canceled) 20.(canceled)
 21. An electrochemical cell comprising an air cathode, theair cathode comprising: a frame; a membrane oxygen electrode attached tothe frame to define a sealed interior cavity; an air inlet communicativewith the interior cavity; and, a liquid outlet communicative with theinterior cavity and positioned lower than the air inlet, wherein theelectrochemical cell further comprises a container containing anoperational body of electrolyte and wherein electrolyte leakage from theoperational body of electrolyte into the interior cavity drains throughthe liquid outlet, wherein the liquid outlet is communicative with areservoir beneath the liquid outlet, wherein the reservoir is locatedwithin an interior of the container.
 22. The electrochemical cellaccording to claim 21, wherein the air cathode further comprises an airoutlet positioned above the liquid outlet.
 23. (canceled)
 24. (canceled)25. The electrochemical cell according to claim 21, wherein the liquidoutlet is positioned at or near a bottom of the air cathode. 26.(canceled)
 27. (canceled)
 28. (canceled)
 29. The electrochemical cellaccording to claim 21, wherein the electrochemical cell comprises aplurality of air cathodes.
 30. (canceled)
 31. (canceled)
 32. (canceled)33. (canceled)
 34. The electrochemical cell according to claim 21,wherein the electrochemical cell comprises a plurality of air cathodes,each air cathode comprising a liquid outlet, and wherein the reservoircomprises a manifold connected to each liquid outlet of the plurality ofair cathodes.
 35. The electrochemical cell according to claim 21,further comprising a pump communicative with the reservoir, the pumpconfigured to transfer electrolyte leakage from the reservoir to theoperational body of electrolyte.
 36. The electrochemical cell accordingto claim 21, wherein the frame comprises a convex top surface andwherein the membrane oxygen electrode is attached to first and secondopposing sides of the frame and attached to the convex top surface inbetween the first and second opposing sides of the frame.
 37. Theelectrochemical cell according to claim 21, wherein the operational bodyof electrolyte is above the air cathode.